Zone 0 (gas) / Zone 20 (dust) is the zone in which an explosive mixture of gas, vapor or dust is continuously present (the gaseous phase inside a receptacle or a closed-off chamber constitutes a Zone 0).

Zone 1 / Zone 21 is the zone in which an explosive mixture of gas, vapor or dust is likely to occur during normal operation. Zone 2 / Zone 22 is the zone in which an explosive mixture is not likely to occur in normal operation, and if it occurs will only exist for a short time (leaks or negligent use).

Encapsulation and flameproof methods to meet the standards. Encapsulation (Ex mb protection) uses epoxy or other resins to totally seal arcing and sparking devices. Flameproof (Ex d protection) contains an explosion, similar to NEC’s explosionproof, and is what is typically used with other electrical boxes installed in hazardous locations.

Flameproof systems and tried and true. Encapsulation is inherent in LED design with no flame path required. It is newer, so typically not part of existing specifications used in industrial lighting. In Appleton LED lighting, the encapsulation method is used.

There is no need to change the luminaire housing between Zone 2 and Zone 1. Also, it lessens the chance of maintenance issues by eliminating the need for a flame path. Flameproof/explosionproof housing is much heavier, so the lighter weight makes installation easier. The encapsulation process also helps the LED lighting last longer.

Compared with other lighting technologies—halogen/incandescent, metal halide, high-pressure sodium-vapor (HPS), fluorescent—LED lighting has no arc hazard, has low surface temperatures, small luminaire cavity requirements, longer maintenance intervals, less maintenance access/failure risk and is the only technology suitable for encapsulation. IEC requires a minimum of 3mm coating thickness to meet the standard with no visible bubbles.

LED drivers can last 100,000 hours although life will decrease at increased temperatures. LEDs do not die abruptly. They tend to fade over time.

Encapsulation technology is relatively new to hazardous location-rated lighting, so many manufacturers and producers have longstanding specifications for flameproof (Ex d) lighting in these locations. The opportunity to use the encapsulation-based protection is due to the inherent solid-state technology. This approach is a significant improvement over conventual flameproofing in:

Product cost: eliminates the need to add heavy metal components

Energy efficiency performance: able to drive LED performance at high levels

Fixture weight and construction: simplified reduction in complexity

Protection from damage: electronics are enclosed in epoxy or potting materials

Given the advantages of LED lighting and encapsulation technologies, it makes sense to revisit these specifications to include Ex mb rated lights as an option.